The bird feeder this second week of January is host to a plethora of Downy and Hairy woodpeckers (and little else). How to identify these species? When both species can be directly compared, like in the middle photo, the Hairy Woodpecker’s larger bulk is obvious. Also compare the bill size. The Hairy’s bill is definitely larger. (Notice that the Hairy Woodpecker in the first photo is banded.)
Here are two not so reliable field marks. In the center photo, notice the black marks on the Downy Woodpecker’s white outer tail feathers. These spots are never present on Hairy Woodpeckers. But notice the white outer tail feathers on the Downy Woodpecker in the bottom photo. Not all Downy Woodpeckers have those spots. Notice also that the red napes on both species can be continuous, and not in two patches, which sometimes occurs in both species.
Despite their similarities, DNA studies indicate these two woodpeckers are not closely related. They remain in the same genus, but Downy Woodpeckers are most closely allied to western Nuttall’s and Ladder-backed woodpeckers. Hairy Woodpeckers are more closely related to Red-cockaded, White-headed and Arizona woodpeckers (Morin in Western Woodlands).